'It was clear that he great ability with the ball but we did have a reservation.

'We just weren’t sure that he was going to be physically strong enough for the Barclays Premier League.

'It was either him or Shinji Kagawa. In the end, we plumped for Kagawa.'

At Manchester City, the issues were different. Roberto Mancini and his coaching staff were convinced of Hazard’s worth but not the money – in the region of £170,000-a-week - they would have to pay him on top of a transfer fee to French club Lille upwards of £32m.

'It was a really tricky one,' said a City insider.

'He was top of our list but the money got silly.

'He was a kid from Belgium playing in a league that is less demanding than the Premier League.

'Ultimately, Chelsea were happy to gamble on the money and we weren’t. He just wasn’t proven enough at the time.'

Battle: Chelsea beat off competition from their Premier League rivals to snap up Hazard for £32million in 2012

Hotly touted: The Belgian winger's form for Lille led to a race from the Premier League's top clubs

Hindsight can make fools of us all, of course. City could argue with some justification that their well-publicised wealth should not force them to cede to rapacious demands. Back in the May of 2012, Hazard’s agent was undoubtedly playing City and Chelsea off against each other and the newly-crowned Barclays Premier League champions did not like it.

'It got ridiculous,' said the City source. 'We were constantly being told: ‘Chelsea will pay this. What about you? We got tired of it.'

United, meanwhile, bought a good footballer in Kagawa. The Japanese international may face a sketchy future under David Moyes at Old Trafford at the moment but he began last season brightly until a knee injury halted his progress.

Making his point: Blues boss Jose Mourinho threatens there is still more to come from Hazard

At full-time at the Etihad Stadium on Monday, however, Hazard certainly began to look value for money. He certainly looked proven, too. His was the starring role in a Chelsea performance that blew apart the myth of invincibility that had begun to build around City, a performance that lit up one of the most memorable nights of the Premier League season so far.

With the City midfield shorn by injury of its organiser Fernandinho, Hazard exploited the spaces and the uncertainty with a ruthlessness not always associated with a young player who has taken time to impose himself consistently on the game in this country.

City full-back Pablo Zabaleta, for example, has not endured a night like it for quite some time and Chelsea manager Jose Mourinho was happy to suggest afterwards that Hazard, who only turned 23 last month, has the opportunity to catapult himself in to the world class bracket.

Outcast: But Manchester United opted to sign Shinji Kagawa instead of breaking the bank for Hazard

'I keep saying he has to improve,' said Mourinho. 'He needs to have his feet on the ground. Ronaldo and Messi are Ronaldo and Messi.

'Eden Hazard is probably the best young player in the world with legs to go there, but give him time.'

Encouraging words from the coach who masterminded City’s dismantling on Monday night and significant, too, given that questions have been asked at Chelsea at times regarding Hazard’s levels of commitment.

Known in west London as the player usually first away from the training ground on a daily basis, Hazard also has something to prove in his home country, too, where the Belgian media are yet to be convinced he can be relied upon in the long-term.

Wing wizards: Chelsea star Hazard seems to dribble down the pitch like a young Ryan Giggs

All Hazard can do is continue to produce performances like the one he served up on Monday. Yesterday, it was tempting to ask who his style is most reminiscent of.

Certainly he seems to glide across the ground a little like Ryan Giggs did in his younger days. He has similarly deceptive pace, too.

Giggs had the odd good day against Manchester City, of course. The best players raise their levels in the really big games. Maybe Eden Hazard will prove himself to be worth all the fuss after all.